Crystallization and Si incorporation mechanisms of SAPO-34

Tan, Juan; Liu, Zhongmin; Bao, Xinhe; Liu, Xianchun; Han, Xiuwen; He, Chaoliang; Zhai, Runsheng

doi:10.1016/s1387-1811(02)00329-3

Cited by 285 publications

(228 citation statements)

References 23 publications

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“…5. All characteristic peaks of the four molecular sieves are identical to those reported in the literature [10], according to which the basic framework vibration frequency region are as follows: the absorption peaks at 490 cm −1 and 632 cm − 1 are T\O bending bands of SiO 4 and D-6 rings, respectively, and the bands at 730 cm −1 and 1095 cm −1 are the symmetric stretch vibration of P\O (or Al\O) and asymmetric stretch vibration of O\P\O, respectively. Moreover, the peak at 1651 cm −1 corresponds to the vibration of hydroxyl groups from adsorbed water on samples.…”

Section: Ft-ir Spectroscopysupporting

confidence: 82%

“…Hydrothermal method, as the conventional strategy, has been applied in the preparation of SAPO-34 by numerous researchers [4][5][6][7][8][9][10][11][12][13][14][15]. However, separation between solvents and solid products is required by filtration or centrifugation, and partial organic SDAs are inevitably preserved in the liquid phase, resulting in the wastewater pollutants and downstream purification system installation [16].…”

Section: Introductionmentioning

confidence: 99%

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Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins

Han

et al. 2014

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a b s t r a c t a r t i c l e i n f oSAPO-34 molecular sieves were fabricated by a dry gel liquid-phase transport method using morpholine (Mor) or morpholine-tetraethylammonium hydroxide (Mor-TEAOH) as the structure-directing agent (SDA). The prepared samples were characterized by scanning electron microscope (SEM), nitrogen adsorption-desorption, X-ray diffraction (XRD), ammonia temperature-programmed desorption (NH 3 -TPD), thermo-gravimetric analysis (TG) and Fourier transform infrared spectroscopy (FT-IR). The results indicated that the dry gel liquid-phase transport method is very effective to fabricate SAPO-34 molecular sieves with average crystal size about 0.6 μm using Mor-TEAOH as SDA and 3 μm using Mor as SDA, respectively. Moreover, the addition of TEAOH is beneficial to produce SAPO-34 with small crystal size. Methanol-to-olefins (MTO) reaction was chosen to test the catalytic performance of as-prepared SAPO-34 catalysts. The prepared SAPO-34 catalyst using Mor-TEAOH as SDA exhibited the excellent catalytic performance in MTO process owing to its small crystal size and high crystallinity. The conversion of methanol and selectivity of ethylene and propylene are up to 100% and 87.9%, respectively.

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Section: Ft-ir Spectroscopysupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins

Han

et al. 2014

Powder Technology

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“…32,33 As indicated in Table 1 In the 29 Si MAS NMR spectra of SAPO-34s (Figure 3c), six resonance signals appear in the spectra. The signals with chemical shift of −90 and −94 ppm, stemming from the coordination states of Si(4Al) and Si(3Al), respectively, show relatively high intensity.…”

Section: −30mentioning

confidence: 93%

Nanosize-Enhanced Lifetime of SAPO-34 Catalysts in Methanol-to-Olefin Reactions

et al. 2013

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In this work, we systematically investigated the size effect of silicoaluminophosphate molecular sieve catalysts SAPO-34 on the catalytic performance of methanol-to-olefin (MTO) reactions. Four highly crystalline SAPO-34 molecular sieves with different crystallite sizes were synthesized under hydrothermal conditions carried out in conventional or microwave ovens with the same starting gel composition using TEAOH as the structure-directing agent. The as-prepared SAPO-34s have similar composition, and their average crystal size can be controlled between 20 nm and 8 μm.Textural properties and chemical environments of framework atoms as well as acid concentration were characterized by N 2 adsorption and NMR measurements. The MTO reactions were carried out over these four SAPO-34 catalysts to study their catalytic performances dependent on the crystal size. The occurrence of catalyst deactivation varied considerably with the crystal size of SAPO-34s. Significantly, the nanosized catalysts, especially the sheetlike SAPO-34 catalyst with 20 nm thickness, exhibited the longest catalyst lifetime and lowest coking rate in MTO reactions. On the basis of the measurement of coke formation and the determination of retained coke species, a scheme is proposed to elucidate the reduction in coke deposition and consequently the remarkably enhanced lifetime on the nanosized SAPO-34 catalysts in methanol conversion.

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“…Our group has reported the crystallization and Si incorporation mechanisms of SAPO-34 hydrothermally synthesized with triethylamine as the template, where the formation of SAPO-34 was ascribed to the contribution of a gel conversion mechanism. 23 Si directly participated in the crystallization since the initial stage and incorporated into the framework of SAPO-34 by SM2 (P substitution by Si) and SM3 (pairs of Al and P substitution by 2Si) mechanisms. In the following study on the crystallization process of SAPO-34 templated by diethylamine, we proposed a model of nonuniform Si distribution in the crystals with the increasing content from the core to the surface.…”

Section: Introductionmentioning

confidence: 99%

Crystallization and Si incorporation mechanisms of SAPO-34

Cited by 285 publications

References 23 publications

Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins

Facile synthesis of SAPO-34 with small crystal size for conversion of methanol to olefins

Nanosize-Enhanced Lifetime of SAPO-34 Catalysts in Methanol-to-Olefin Reactions

Investigation of the Crystallization Process of SAPO-35 and Si Distribution in the Crystals

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